A great variety of drip irrigation devices are known in the patent literature and are presently in use. Included among these are devices described and claimed in applicant's earlier issued Israel Patents and Patent Applications 41324, 46706, 48810, 52454, 55185 and U.S. Pat. Nos. 4,175,882, 4,195,784 and 4,126,998.
Recently it has been suggested by applicant and others to use a relatively thin plastic sheet in the formation of a continuous irrigation tube having pressure reducing pathways distributed therealong in communication with a water conduit. This general concept is shown in Israel Pat. Nos. 44810 and 52454 of applicant and applicant's aforesaid U.S. Pat. Nos. 4,175,882, 4,195,784 and 4,126,998 as well as U.S. Pat. Nos. 3,873,030, 3,896,999 and 4,047,995.
In particular, U.S. Pat. Nos. 3,873,030 and 3,896,999 to Barragan illustrate a drip irrigation device employing a flexible sheet to define a water conduit and molded attachment members defining a pressure reducing channel laminated to the water conduit. U.S. Pat. No. 4,047,995 to Leal-Diaz shows a continuous irrigation hose in which the pressure reducing path is defined along an edge thereof by an embossing technique.
In the patent to Leal-Diaz as well as in the patents to Barragan, the water flow channel must be apertured in order to provide a communication pathway between the water flow channel and the pressure reducing pathway for water to enter the pressure reducing pathway. The provision of such an aperture is often inconvenient and may require a high degree of alignment and sophistication in the production process.
Applicant describes in U.S. Pat. No. 4,195,784 drip irrigation apparatus comprising a plurality of thin foils in which the aperture may be produced by stamping, laser radiation or any other hole making technique.